Fuel control systems for turbines have been proposed in, for example, U.S. Pat. Nos. 3,418,805, 3,660,977, and 4,033,115; however, none of the proposed fuel control systems provide effective long term storage of the fuel in the fuel control system, rapid start and operation of the turbine, and modulated fuel flow to the turbine, all of which are factors of extreme importance in, for example, emergency hydraulic power systems for aircraft
While proposed gas turbine engine control systems employ, for example, servo valves and fuel pressure differential valves, a disadvantage of the proposed control systems generally resides in the location of the servo valve in the control system, and ineffective means for insuring a proportional fuel flow to the gas turbine engine independent of the pressure of the fuel tank or turbine engine pressures.
In, for example, emergency hydraulic power systems for aircraft, it may develop that the small gas turbine propulsion units for the emergency hydraulic power systems may either be stored for a long period of time, for example, up to ten years, or use of the propulsion units may not be required for a considerable length of time; however, as can be readily appreciated, when the propulsion units are necessary, it is extremely essential that the fuel control system rapidly becomes effective with a modulated fuel flow so as to insure a proper operation of the propulsion unit.